Hello.
How to define structures before using them in each other.
main.cpp:
Compiling with command: g++ main.cppCode:#include <iostream> using namespace std; struct Struct2; struct Struct1; struct Struct2 { Struct1 a; } struct Struct1 { Struct2 b; }; int main() { }
Errors:
main.cpp:10: error: field `a' has incomplete type
main.cpp:17: error: multiple types in one declaration
Thanks in advance.
for c use gcc and .c extention
C has no automatic typedef
you can define pointer to undefined structCode:struct Struct2; struct Struct1; struct Struct2 { struct Struct1* a; }
but if you want to add struct as object - it should be fully defined, otherwise compiler cannot know its size.
What you trying to do will require from the compiler to build endless loop of structs inside structs. It is impossible to do. This data strycture will require infinite memory size
All problems in computer science can be solved by another level of indirection,
except for the problem of too many layers of indirection.
– David J. Wheeler
... It stil lwon't compile. Even though it will not produce an infinite loop.Code:#include <stdio.h> struct Struct2; struct Struct1; struct Struct1 { Struct2 a; } struct Struct2 { int a; } int main() { }
One of them has to be a pointer to a struct, not an instance of the struct.
Otherwise, the mutual recursion of the struct uses up all available memory!
You only need
struct foo;
in order to be able to declare a pointer to it.
At this stage, this is called an incomplete type.
But you need the whole thing in order to be able to create an instance of that struct.
If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
If at first you don't succeed, try writing your phone number on the exam paper.
Ok, thanks.
